1. Field of the Invention
The invention relates to an optical system and a display apparatus, and particularly relates to an illumination system and a projection apparatus.
2. Description of Related Art
With the progress of modern video technology, optical projection apparatuses have been widely used in the occasions of home theater, small conference report, and discussion. An optical projection apparatus includes an illumination system, a light valve, and a projection lens. The light source is configured to provide an illumination beam, the light valve is configured to convert the illumination beam into an image beam, and the projection lens is configured to project the image light beam onto a screen to form an image.
Generally speaking, the conventional illumination system in the optical projection apparatus usually use a set of red, blue and green light emitting diodes having the same having the same illuminating areas and dispersion angles as the light source of the illumination system. In other words, since these light emitting diodes have the same illuminating areas and dispersion angles, they also have the same E'tendue. Thus, by using a light consolidating unit and a collimating lens, the light beams provided by the light sources can be effectively collected and transmitted to the light valve. However, under such circumstance, the choice on light sources is very limited, and it is unable to choose a light source having a desirable optical performance but having a different illuminating area and dispersion angle.
Besides, if the light source having a desirable optical performance but having different illuminating area and dispersion angle is chosen as a different light source in the illumination system, the light beam provided by the light source is unable to be effectively connected and transmitted to the light valve due to the difference in E'tendue. In this situation, the color temperature balance and light output efficiency of the red, green, and blue light beams output by the illumination system are thus influenced.
U.S. Pat. No. 8,098,375 has disclosed an illumination system, including one or more light emitting diodes or light emitting diode array modules, a light splitter, and an optical concentrator. In addition, the optical concentrator may be a compound parabolic concentrator (CPC), a compound hyperbolic concentrator (CHC), a compound elliptical concentrator (CEC), or a taper optical tube. US Patent Publication No. 20070280622 has disclosed a light source assembly including a light guide element at the center of the optical axis. U.S. Pat. No. 8,684,555 has disclosed a light transmitting apparatus including a first light emitting diode and a first converter substance.
The information disclosed in this BACKGROUND section is only for enhancement of understanding of the BACKGROUND section of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the BACKGROUND section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.